I am using a liquid detergent and I use exactly the half of the detergent they say I should use. If a the washing machine requires 1 cup, I do half. Mostly because I don’t trust the company to put me over their interests.
Now, what will happen? Will my clothes end up staying dirty? Will it not remove stains which a full cup would have removed? Will surfexcel kidnap me and torture me for not obeying their commands? Help meeee!!
Theres no way to figure out what will happen or what the optimum amount of detergent is because it can depend on a lot of things like the fabric (type, color), type of stain (oil, dirt, paint, ink etc), detergent formulation, washing machine, water (minerals/tds and temp) etc. The worst that can happen is permanent stains on your clothes but that can sometimes happen even if you use the right amount. You clothes might also not smell as strongly of detergent but that doesnt mean they arent clean.